Trackway and seed ?
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Seed ? (pictures 2 and 3)
While collecting fern fossils from a Carboniferous coal seam and
associated shale, I came across what appears to be tiny tracks....insect
or another tiny arthropod? They are in pairs with about 1cm between
the two parallel rows and a "stride" of about 1.5cm. These appear to
be on-purpose and not a geological oddity. The tracks also show up
on other parts of the matrix.....always in pairs. Now I didn't pick up this
particular rock because of the tracks........my eyes aren't THAT good.
Rather, I picked it up because of what looks to be a large seed on the
other side. I didn't discover the tracks until I returned home. I hope I was
able to capture the tracks well enough in my photos. Any and all opinions
and comments are welcome.
1. Not being an expert on trackways but familiar with the markings or rootlets
I suggest (for the matter of discussion) the trackway might represent small holes
once occupied by the rootlets of a Stigmaria root? There are also some more
of these markings to the right of the scale which indicates a more random pattern.
2. Isn't it odd that even the markings to the right of the main assemblage are still in pairs?
Pairs that are spaced again, 1cm apart. To my eye, they really look to be "on purpose",
not a random collection of marks.
3. I'm not saying the "trackway" is random but suggesting that the little pits are visible on
the matrix other than in the straight line. Could the trace fossil represent a trackway .... sure.
However, the speculation comes from the lack of obvious features.Trace fossils are
fascinating and many require a vivid imagination to explain and often controversial. If not
obvious then we all speculate as to what could have made the interesting pattern of pits. We
are looking at a small chuck of Carboniferous mud with impressions we don't instantly recognize.
4. Imagine something else "on purpose" ...a single pair of waterlogged twigs hanging down
from a floating mat of pond scum? Each time a ripple raises the mat the twigs leave another
pair of tracks as the mat fragment slowly moves "northeast" on the incoming tide (this is after
all the margin of the old ocean?)...the parallel "set of tracks" running "southwest" would have
been left on the outgoing tide...sedimentologists refer to these as "prod" or "tool" marks; and
they can look pretty convincingly like fossil footprints!
5. Indeed, prod marks like these are useful to determine paleo-current and -wind directions
from compass-oriented specimens, if their significance can be ascertained on the outcrop;
I wonder if anyone has done any work on your collecting site previously?
6. Work has been done on the general area. This is not a "site" in the traditional sense. There
is no outcrop. Rather, I'm picking through a tailings pile about the size of a small apartment
building left over from coal mining many years ago in the anthracite region of NE Pennsylvania.
I've collected various ferns, Neropteris, Calamites, Chordates, but this is the first non-botanical
that I've found there.
7. I certainly can't say yea or nay whether it is a trace fossil, but that would be a good tentative
identification. The "seed" looks like a siderite nodule to me. I do not see any external structural
features that cry out "seed." In the fossil plant exhibit currently at the Falls of the Ohio State Park,
we have a seed fossil from the Mississippian. It is pretty large (~1") olive-shaped with longitudinal
striations and has a short stem at one end.
8. If someone would say that the "trackway" was a true trackway of a tiny newborn amphibian ...
then the next question would be ... what features indicate it is an amphibian trackway? Followed
by what documentation (with images) is there on this particular trackway. If someone would say
that it's not a trackway then the question would be ... why is it not a trackway and what does it
represent? Followed by a questions regarding resource material. When dealing with what appears
to be tiny impressions ... Speculations are often the best we can hope for. Reading what others
speculate is stimulating. Here is a fun page I built on the subject of trackways. Click Here
9. Thanks for the neat way of showing us how simple it is to speculate on what may have made
a trackway, and then find out what really made it. There are so many times we have seen something
that looked like a trackway in the field, and have guessed at what may have made it... but never
knowing. I have to admire those persons that are into trace fossils. The questions could take up an
entire lifetime of research with few answers.
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